Process for separation of



Nov. 19, 1935. M. H. TUTTLE Re.`19,763

PROCESS FOR SEPARATION 0F MINERAL OIL Original Filed Dec. 22, 1932 ATTORNEYS Ressued Nov. 19, 1935 UNITED STATES PROCESS FOR SEPARATION OF MINERAL OIL Malcolm H. Tuttle, New Rochelle, N. Y., assigner to`Max B. Miller & Co. Inc., New York, N. Y., a corporation oi" Delaware Original No. 1,912,349, dated May 30, 1933, Serial No. 648,383, December 22, 1932. Application for reissue July 3, 1934, Serial No. 733,620

24 Claims.

This invention relates to a process for the separation of mineral oil into fractions which are respectively more parainic in composition and characteristics and more naphthenic in composition and characteristics than is the original oll and which may have similar boiling ranges.

Mineral oils comprise naphthenic constituents and parafiinic constituents which have different characteristics that are known to a considerable extent; and these constituents impress their characteristics upon the oil to a degree depending upon the'proportion in which they are present in the oil. Oils comprising a relatively higher proportion of paraflinic constituents are commonly called paranic base oils, an example thereof being oils from the Appalachian field; and oils containing a relatively lower proportion of parafilnic constituents and therefore a relatively higher proportion of naphthenic constituents are commonly called naphthenic or asphaltic base oils, an example of such oils being obtained from gulf coastal or Mexican vfields;

and oils containing an intermediate proportion of paraflinic constituents and also containing naphthenic constituents are commonly called mixed base oils, an example of such oils being oils from the mid-continent elds. Parailinic oils having a given viscosity have lower specific gravity, a higher flash test, -a smaller change of viscosity with changes in temperature and a higher ratio of hydrogen to carbon than do naphthenic oils of the same viscosity. Parafllnic oils are more stable and more desirable as lubricants, particularly under conditions involving high temperatures' and extensive changes of temperature, than are oils in which parainic constituents are present in relatively lower proportion and naphthenic constituents are present in relatively high proportion. The characteristics of mid-continent or mixed base oils are intermediate the characteristics of paraiiin base and asphalt base oils.

Naphthenic oils are preferable to paraiiinic oils for somev uses, such as insulating oils for electrical apparatus and lubrication of chains and of gearingnot subjected to low temperatures.

An object of this invention is to provide a process whereby mineral oils may be rapidly and economically separated into fractions which are respectively more parafilnic and more naphthenic in. composition and in characteristics than is the original oil, the separation being eected regardless of whether the-oil has previously been subiected vto acid treatment or dewaxing treatment or b oth, and without chemical reaction and without formation of sludge, to the end that solvents employed to eiect such separation may be used indenitely and losses minimized.

A speciilc object of this invention is to provide a method whereby oils obtained from mixed base petroleum may be separated into fractions of whichat least one is a lubricating oil stock having viscosity-gravity characteristics and viscosity-temperature characteristics similar to or equalv to or better than such characteristics of oil stocks having similar viscosity and obtained by usual distillation from crude oils from the Pennsylvania field, a further object being theA production from decidedly naphthenic or asphaltic oil of an oil fraction of which the characteristics are `at least substantially more parailinlc than the characteristics of the original oil.

To assist in understanding the effects and results of the practice ofzthis invention, reference may be made to certain values'l commonly em- 2o ployed to indicate the character of oil. Thus the relation of viscosity to specific gravity is indicated by the viscosity-gravity constant determined in accordance with the following equation:

where \a=viscosltygravity constant V'=Saybo1t viscosity at 210 F.

:specific gravity an 60 r'. 3

Pennsylvania lubricating oils have a viscositygravity constant falling between approximately .807 and .827; mixed base mld-continent lubricating oils have a viscosity-gravity constant fall- 35 ing between approximately .827 and .867; and naphthenic or asphalt base lubricating oils from the gulf coast and California have a viscositygravity constant falling between approximately .867 and .887. However, specic oils from one 40 eld will have a viscosity-gravity constant falling within the 'range above given for-another field. Moreover, the relation of temperature to viscosity is measured by a viscosity index in which Pennsylvania oils have a value of 90 to 100 and oils of 45 and unstable unsaturated hydrocarbons, but such 5 treatment involves chemical reaction and production of sludge from which the recovery of asphalt is diiiicult and uneconomical, and loss of paraiilnic constituents carried down with the It has been proposed heretofore to divide mineral oil containing naphthenic and parafllnic fractions into fractions more paraiiinic and more naphthenic than the original oil by extracting the oil with nitro-aromatic solvents, which may be.

termed naphthenic solvents inthat they have greater solvent power for naphthenic constituents than for parafllnic constituents, the mixtureseparating by gravity into an upper layer comprising the more paramnic fraction and some of the solvent and a lower layer comprising the more naphthenic fraction dissolved in a major proportion of the solvent. Such treatment of mixed base oils having a high or intermediate asphalt content, and particularly such treatment of the residue of such oils, by the use of selective solvents heretofore proposed has proven impracticable or has failed. The apparent cause is that the solvents proposed when used in proportions determined by economical considerations appear to be mlscible with residual oilsof high or intermediate content of naphthenic constituents or asphalt, with the result that the necessary separation into layers does not occur. It appears that the nitro-aromatic solvents form with the asphalt or with the liquid naphthenicconstituents, ,or with both, a mixture having extensive solvent power for paralnic constituents. Cresylic acid has selective solubility for naphthenic constituents, but when used in sumcient proportion to take a substantial proportion of naphthenic constituents into solution, in an effort to divide oil into naphthenic and parailinic fractions by extraction, it has a substantial solvent power for paraiilnic constituents.

I have found that mineral oil containing parafllnic and naphthenic constituents can be separated into fractions respectively more parainic and more naphthenic than the original oil by subjecting the oil to contact with cryslyic acidv in the presence 4of a solvent which has greater solvent power for paraiinic constituents than for naphthenic constituents, the treatmentpreferably being applied under such conditions that the solvents employed are mutually miscible to only alimited extent. It appears that under such conditions, the normall selectivity of cresylic acid for naphthenic constituents is increased or its solvent power for paraihnic constituents is decreased, particularly when the solvent of parafhnic constituents has limited solubility for and in the cresylic acid; and it appears also that the selectivity of 'the solvent for paramnic constituents is increased or its solvent power for naphthenic constituents is decreased in the presence of cresylic acid. When the oil is contacted with cresylic acid in the presence of such a -parafllnic solvent, separation occurs promptly and readily.

In accordance with this invention, therefore, mineral oils are separated into fractions respectively more paramnic and more naphthenic than the original oil by extracting the oil with cresylic acid in an operation in which at least some part of the contacting of the oil with cresylic acid occurs in the presence of a solvent having greater solvent power for parafiinlc constituents than for naphthenic constituents. In the presence of such solvent, the tendency vof the cresylic acid, when present in sumcient proportion to eiIect substantial extraction or solution of the naphthenic constituents, to take into solution a substantial proportion of the parainic constituents, is minimized; and there is produced from a mixed base or naphthenic oil a fraction having'characteristics similar to or equal to or better than the characteristics of a similar fraction obtained from paraiiln base oil, or there is produced a fraction having characteristics at least markedly more paramnic than the original oil. Thus, the extraction of the oil with cresylicfacid in the presence of a paraiiinic solvent produces results heretofore unobtainable by the use of cresylic acid alone. 10

Commercial cresylic acid comprises orthocresol, metacresol, paracresol, phenol and xylenol and a reference herein to cresylic acid is intended as a reference to such 'acid or to those components thereof or'to mixtures of any two or more of those components. Such substances can readily be removed from the oil by distillation at temperatures which do not tend to decompose the oil or the substances.

By way of explanation, cresylic acid. unless 20 mixture; the percentages of phenol and such 25 other substances vary but are ordinarily comparatively small; for instance, the phenol may constitute a few percent of the total cresylic acid, while other substances may be present only as impurities.

Parafiinic solvents suitable for use in the practice of this invention include ethane, propane, butane, pentane, natural gasoline and light naphtha, such light nephtha preferably being preliminarily treated with a solvent, such as cresylic acid, having a selective solvent power fornaphthenic constituents of oil. Such parailinic solvents have a limited solubility in and for cresylic acid and a' greater solvent power for parafllnic constituents of oil thanfor cresylic acid and they 40 'In the practice of this invention, the oil to be 5 divided into fractions is, at least at one point in the treatment thereof, contacted simultaneously with cresylic acid and a parafiinic solvent and such contacting may be effected in a batch operation, or in a continuous operation in which there 5( is preferably maintained a counter-flow of solvents while the oil is introduced to such counteriiow at an intermediate point thereof and the naphthenic fraction is taken oil at a point on the same side of oil as the point of introduction ofthe paraiiinic solvent and the naphthenic fraction is taken ofi at a point on the opposite side of the point of introduction of the oil.

The solution of. naphthenic constituents is g. heavier than the solution of paraflinic constituents and in the separating operation the solution of paraffinic constituents forms ultimately an upper layer and the solution of naphthenic constituents forms ultimately a lower layer. In o continuous extraction, the separation occurs in the counter-flow system. The solution of the paraiiinic fraqtion will comprise paraiilnic constituents andfnaphthenic constituents in a ratio substantially greater than the ratio of paramnic 7 constituents to naphthenic constituents in the original oil and it will contain the major portion of the parafllnic solvent and some of the naphthenic solvent. The solution of naphthenic constituents will include naphthenic constituents and 1 the point of introduction of the 5;

paraflinic constituents in a ratio greater than Y y the ratio of naphthenic constituents to parailinic of the oil in the solvent or-solvents may be effected by heat or agitation or botli. Prior to the separation it is preferable that the temperature should be suiciently high to promote the solvent action of the solvents upon the constituents of the oil, but during the separation it is desirable that the temperature should be such as will promote such separation. Low temperatures promote separation, but the temperature should not be so low as to effect solidiflcation of any of the solvents. Moreover, in the treatment of wax-containingoil the mixture of solvent and oil should at some time before separation possess a temperature at which the wax is all in liquid state, but the separation may be made thereafter at a temperature at which a part of the wax is solidified. The presence of the parailinic solvent permits the wax present to precipitate in particles separate from each other and from the oil, giving a mixture which is uid and in which the oil is free and ready to be acted upon. Thus the oil may be mixed at a temperature above the melting point of the oil, with a portion of either of the solvents thathas not been cooled orhas been warmed; and after the mixture is cooled it may be introduced to the action of counter-flowing solvents which arel at a temperature which promotes separation.

In the practice of this invention, the lighter is the paramnic solvent, the greater is the specific gravity diierence between the solution of'parailinic fraction and the solution of naphthenic fraction, .and the greater is the tendency for separation of the solutions to occur; and the extraction operations will be conducted under such conditions of temperature and pressure, con-V sistent with the foregoing, that the solvents employed are in liquid phase. In the practice of this invention, a batch extraction step or a continuous extraction step may be repeated as often as may be necessary to impart to the 'resulting products the parainic and naphthenic characteristics respectively desired for those fractions, or a continuous extraction step`= may be extended for` a similar reason.

Thus, a feature of this invention is that the oil to be treated, which may be a distillate or a residue and Amay or may not have previously been rened or dewaxed, may be subjected simultaneously to contact with cresylic acid anda parafnic solvent.

A further feature of this invention is that cresylic acid alone may be caused to be capable of eiiecting division in fractions respectively more paraillnlc and more naphthenic an oil which would not otherwise separate into two layers when treated with cresvlic acid alone. In accordance with this feature of this invention the oil is first contacted with cresylic acid alone.

The solution of oil constituents in cresylic acid is then extracted with a parafiinic solvent as above set forth, theol] constituents thus being simultaneously contacted with both paraflinic and naphthenic solvents. The paramnic solvent and oil constituents in solution' therein is then separated from the naphthenic solvent which contains. naphthenic constituents in solution, and freed ol' paraiiinic solvent. The paraiiinic constituents so obtained, and such naphthenlc solvent and constituents as are contained therein. are then introduced to the oil flowing to contact with the cresylic acid. 'I'he parailinic oil constituents so added to the oil to be treated render that oil mixture capable of being divided by cresylic acid alone into a paraiiinic fraction and a solution of oil constituents in cresylic acid. which fraction and solution separate readily into two layers. The upper layer of this separation is freed of cresyllc acid and constitutes the desired p araiiinic fraction.l Apparently the increasing of the concentration of paraflinic constituents in the original oil renders it separable by use of cresylic acid alone when it would not otherwise be separable by that solvent alone.

The naphthenic and paraflinic solvents may be used in widely varying proportions, the proportions found effectivel in practice being one to three parts by weight of naphthenic solvent and one to three yparts by weight of paraiilnic solvent to each part of oil to be treated. In view of the wide variations in the properties of oils from different sources, the most economical proportionswhich produce fraction of desired character should be determined by test of the oil to be treated.

Moreover, it is contemplated that in the practice of this invention the effectiveness of cresyllc g5 acid or components thereof as naphthenic sol- -vents may be increased by mixing therewith a suitable proportion of solvents which have a selective solvent power and definite selectivity for naphthenic constituents and a limited solvent power for mineral oil constituents, and dissolve preferentially asphalts and those constituents of the oil which are of higher molecular weight. `Examples of such solvents are sulphur dioxide, furfuraL'pyridine, and aniline,and inasmuch as u they preferentially disolve asphalts and constituents of higher molecular weight but have a limited solvent power for mineral oil, they do not have that tendency to be miscible in all proportions with mixed base oil of high asphalt content, which tendency is possessed by dinitroaromatic solvents.

In the drawing:

Fig. l is a iiow sheet indicating the steps in the direct treatment of oil in accordance `with this invention; and

Fig. 2 is a iiow sheet indicating the steps in the modified procedure above mentioned.

While the inventionv may be carried out by the treatment of separate batches of oil, there are indicated in Fig. 1 the steps whereby continuous treatment of mixed base oils may` be effected. The oil to be treated which may be either a distillate or a residue, is oontactedwith cresylic acid or with one or more of its components at a temperature which causes the mixture to separate intolayers. In the procedure illustrated, the-untreated oil is continuously introduced into a' contacting chamber operation preferably at an intermediate level and cresylic acid or'one or more of its components is introduced into that chamber at a suitable rate at an upper level thereof and from a similar level there is. withdrawn naphthenic' fraction ,A

which is passed into a second contacting operation, preferably at an upper level thereof, info which propane is introduced at a suitable rate, preferably at a lower level thereof, while there is withdrawn therefrom naphthenic fraction B and paraiinic fraction B which is continuously' returned to the first contacting operation, preferably at a lower level thereof. Parafiinic fraction A is treated for the removal of propane as by the reduction of the pressure upon the fraction or by the application of heat or by both of such steps. The propane is passed to propane storage While the residue of paraflinic fraction A is subjected to heat to effect distillation therefrom of the cresylic acid which is passed to cresylic acid storage. The residue of the paraifinic fraction A constitutes the desired parafinic oil. The contacting step to which is introduced naphthenic fraction A and propane, is so conducted as to ef- :ect counter-flow with the result that the propane removes paraflinic constituents from naphthenic fraction A and carries them back to the main contacting operation, thus providing in the main contacting operation a counter-flow of parafilnic and naphthenic solvents', to a mid-point of which the oil is introduced. Naphthenic fraction B is treated for the vaporization of propane as by reduction of pressure or application of heat or both of such steps, and the propane is passed to propane storage while the residual mixture is subjected to distillation forthe removal of cresylic acid, the residue of naphthenic fraction B constituting the desired naphthenic oil. Contacting chambers employed are preferably packed-to promote agitation and contacting and they may be separate as indicated in the drawing or joined together.

Referring to Fig. 2 of the drawing, the oil to be treated is first contacted with cresylic acid;

and the cresylic acid containing oil constituentsin solution is then passed into contact with propane or other paranic solvent which effects a washing of the heavy fraction of the rst contacting step. The resulting solution of paraflinic constituents and of small quantities of naphthenic constituents and cresylic acid in the parafnic solvent separates readly from the solution of naphthenic constituents in cresylic acid. After separation it is treated for the removal of parafiinic solvent and then added to the oil flowing to the original contacting step for immediate contact with cresylic acid alone. 'I'he treatment with cresylic acid then leaves a substantial paraffinic fraction undissolved and that parailinic fraction forms an upper layer and is removed and is freed from cresylic acid and constitutes the desired parafiinic oil. The naphthenic fraction, after treatment with the paraifinic solvent and removal of the paraflinic solution, as above stated,

is treated for removal of solvents and constitutes the desired naphthenic fraction.

The pressures and temperatures necessary in order that solvents which are in vapor phase at normal temperature may be maintained in liquid phase during use may be determined by referi ence to existing pressure and temperature tables.

In the practice of this invention, the parafiinic fraction produced is more paraifinic than the original oi l and the naphthenic fraction produced is more naphthenic than the original oil, and those two fractions are respectively more parafnic and more naphthenic than any fractions obtained by the use of cresylic acid alone.

The paramnic fraction may be subjected to any desired treatments such as acid treatment, clay treatment and dewaxing for the purpose of providing finished lubricants, it being ldesirable in some cases to treat the parafiinic oil with a caustic soda solution, e. g.' 5%, for the removal Vof tracesl of cresylic acid before such further ccnstantof 0.845, was treated in continuous.

counter-flow contacting chambers at a temperature of 24 F. using two pounds of commercial cresylic acid and two pounds of propane per pound of original oil, and the resulting products had, after removal of the solvent, the following characteristics z Un- Naphtreated Pagfn thenic oil oil Specific gravity @i F 9236 B888 i. 008 Viscosity S. U. at 210 F 148.0000 98. 0000 460. 000 vViscosity-gravity constant 0. 845 0. 807 0.941

Yield volume 70. 8 28. 2

inal oil and greater than the viscosity-gravity constant of suchmarkedly naphthenicI or asphaltic base lubricating oils as oils obtained from the gulf coast a'nd California.

The procedure wherein parafiinic and naphthenic solvents are simultaneouslyemployed and the advantages thereof are more at length set out in my cca-pending application, Serial No. 623,483, filed July 20, 1932. f

It is intended that distillates and residue, refined or unreflned, may be treated in accordance with this invention, this invention being of special importance in the treating of lubricating oils for the improvement of the characteristics thereof. It is to be understood that this invention is not to be limited by any theory of operation expressed or by any example given and that it includes all modifications and variations falling within the appended claims.v

I claim:

1. In the art of refining mineral oil comprising naphthenic andparaflinic constituents, the step comprising extracting the oil, in the presence of an added liquid having greater solvent power for paraflinic constituents of the oil than for naphthenic constituents thereof, with cresylic acid, the said paraiinic solvent and the cresylic acid being adapted to form a two liquid phase 7 a boiling range substantially below the boiling point of the oil, with cresylic acid comprised principally of cresols, the said hydrocarbon solvent and the cresylic acid being adapted to form a two-layer solvent system.

3. In the art of rening mineral oil comprising naphthenic and paraiilnic constituents, the step comprising extracting the oil, in the presence of an added hydrocarbon of the group consisting of ethane, propane, butane, pentane, natural gasoline, low end-point naphtha, and a mixture of two or more thereof, with4 commercial cresylic acid, said added hydrocarbons and cresylic acid being adapted to i'orm a two-layer solvent system.

- 4. In the art oi' refining mineral oil comprising naphthenic and paraillnic constituents, the step comprising extracting the oil in the presence of a'liqueiied normally gaseous hydrocarbon with cresylic acid consisting principally of cresols and containing relatively small proportions of other ingredients occurring in commercial cresylic acid, the said hydrocarbon and cresylic acid being adapted to form a two-layer solvent system when contacted with each other.

5. In the art o1' rening mineral oil comprising naphthenic and parafiinic constituents, the step comprising contacting the oil with cresylic acid, and contacting the solution of oil constituents in cresylic acid with a solvent having greater solvent power for paraiiinic than for naphthenic constituents oi' the oil, the said cresylic acid and paraffin solvent being adapted to form a twolayer solvent system when contacted with each other.

6. In the arto! refining mineral oil 'comprising naphthenic and paramnicconstituents, the step comprising contacting the oil with cresylic acid, and contacting the oil not dissolved thereby and the solution thereby formed with a, solvent having greater solvent power for paraillnic than for naphthenic constituents of the oil. said cresylic acid and parailln solvent being a/dapted to form a two-layer solvent system when contacted with each other.A

'1. In the art of reiining mineral oil comprising naphthenic and paraflinic constituents, the step comprising contacting the oil with cresylic acid, contacting the solution of oil constituents in cresylic acid, with a solvent having greater solvent power for parailinic than for naphthenic constituents oi' the oil, and passing the solvent and oil dissolved therein into the mst-mentioned contacting step, said cresylic acid and paraffin solvent being adapted to form a twolayer solvent system when contacted with each other.

8. In a process of producing lubricating oil, the steps comprising extracting a residue of midcontinent petroleum with cresylic acid in the presence of a solvent having greater solvent power for paraiiinic than for naphthenic constituents of the oil, and separating said solvent and cresylic acid from the resulting fractions, said cresylic acid and vparaffin solvent being adapted to form a two-layer solvent system when contacted with each other.

9. In a process of producing lubricating oil, the step comprising extracting the residue of a midcontinent petroleum with cresylic acid in the l presence oi' an added parafiinic solvent to produce fractions of the oil respectively richer in paraiilnic and naphthenic constituents of the oil, said cresylic acid and paramn solvent being adapted to form a two-layer solvent system when contacted with each other.

10. In the art of refining mineral oil comprising naphthenic and parainic constituents, the steps comprising contacting the oil with a solvent having greater solvent power for paraillnic than for naphthenic constituents of the oil, and contacting the resulting solution of oil constituents with cresylic acid, said cresylic acid and parailln solvent being adapted to form a two-layer solvent system when contacted with each other. 5

11. In the art of rening mineral oil comprising naphthenic and paraflinic constituents, the step comprising contacting the oil with cresylic acid. contacting the solution of oil constituents in cresylic acid with a solvent having greater solvent power for paraiiinic than for naphthenic constituents of the oil, separating the solvent and substances in solution therein from the remainder. of the solution of oil constituents in cresylic acid, removing the solvent from the substances in solution therein, and returning said substances to the oil passing to the rst-mentloned contacting step, said cresylic acid and paraiiin solvent being adapted to forma two-layer solvent system when contacted with each other.

l2. In the art of rei'lning mineral oil, the step comprising extracting the oil with a mixture of cresylic acid and sulphur dioxide in the presence of a solvent having greater solvent power for paraflinic than for naphthenic constituents of 26 the oil, the said mixture of cresylic acid and sulphur dioxide, when contacted with the said paraiiinic solvent, being adapted to form a two-layer solvent system.

13. A process of rening a mineral oil which 30 comprises counterflowing a solvent selective for parafn'ic constituents of the oil and cresylic acid, and, introducing the oil to the counterfiowing solvents at a point intermediate the points where the solvent andcresylic acid are introduced.

14. A process of refinmg a residual mineral oi1 which comprises counterowing a solvent selective for parailnic constituents of the residual oil and cresylic acid, introducing the oil to the counterilowing solvents at a. point intermediate 40 the points where the solvent and cresylic acid are introduced, withdrawing a relatively parafflnic fraction adjacent the point where the cresylic acid is introduced,l and withdrawing a relatively naphthenic fraction adjacent the point where fresh solvent is introduced. f'

15. A process of refining a mineral oil which comprises treating said oil conjointly with a solvent selective for paraiiinic constituents of the oil and with cresylic acid having intermingled therewith one of the group of substances consisting ofpyridine, aniline or furfural, under conditions adapted to cause the oil and solvents to separate into layers, and separating the layers.

16. In a process of producing lubricating oil, the steps comprising extracting a residue of petroleum with cresylic acid in the presence of a solvent having greater solvent power for paraflinic than for naphthenic constituents of the oil, and separating said solvent and cresylic acid from the resulting fractions, said cresylic acid and soivent being adapted to form a two-layer solvent system when contacted with each other.

17. In a process of producing lubricating oil, the steps comprising extracting a residue of a mineral oil which is more naphthenic than oils from Appalachian iields with cresylic acid in the presence of a solvent having greater solvent power for paramnic than for naphthenic constituents of the oil, and separating said solvent and cresylic 7o acid from the resulting fractions, said cresylic acid and other solvent being adapted to form a two-layer solvent system when contacted with each other, i

18. The process as claimed in claim 1 wherein 75 the added liquid consists mainly of hydrocarbons having less than five carbon atoms and a vapor pressure markedly higher than gasoline.

19. The process as claimed in claim 1, wherein the solvent and cresylic acid are employed in amounts in the order of double the weight of the 20. In the art of refining mineral oil by means of a parafnic solvent and a naphthenic solvent, the steps comprising separating a naphtheic extract from the oil, separating a portion of the extract from the balance thereof by-means of w paralnic solvent, removing parai'lnic solvent added liquid having greater solvent power for paramnic constituents of the oil than for constituents soluble in the cresols, separating the mixture into layers, and separating the layers.

22. The process of rei'lningmineral oil which comprises treating it conjointly with a'relatively light hydrocarbon solvent and with another'solvent composed primarily of cresols, permitting the mixture to separate into layers, separating the layers, and recovering the solvents.

23. In the art of refining mineral oil comprising naphthenic and parafilnic constituents, the

steps comprising contacting the oil to be treated with. a naphthenic solvent heavier than the oil to be treated, separating from the mixture thus produced naphthenic solvent containing oil constituents in solution, contacting the separated naphthenic solvent and oil constituents with a pararlinic solvent, separating from the mixture thus produced paralnic solvent containing oil constituents in solution, removing the parainic solvent from the mixture separated in the last preceding step, andreturning the resulting oil constituents to contact with the oil and naphthenic solventin the first recited step, said naphthenic solvent and parafilnic solvent being adapted to form a two-layer solvent system when contacted with each other.

24. In the art of rening residual mineral oil containing naphthenic and paraffinic constituents, the steps comprising-rst contacting the oil to be treated with naphthenic solvent heavier than the oil to be treated, separating naphthenic solvent containing oil constituents dissolved therein from the mixture thus produced, contacting the separated naphthenic solvent containing oil constituents with liquefied propane employed as a paraflinic solvent, separating propane and oil constituents in solution therein from the remainder of the mixture produced in the last preceding step, vaporizingpropane from vthe thus separated propane solution, and returning the constituents from which propane has been vaporized to the rst mentioned contacting step, said naphthenic solvent and propane being adapted to form a two-layer solvent system when contacted with each other;

' MALCOLM H. TU'I'I'LE. 

